Docs could use a little better navigation interface

There is no "up" button which takes you to the enclosing section. For example on these pages you can only go "back" and "forward:"
https://www.boost.org/doc/libs/1_69_0/libs/gil/doc/html/design_guide.html
https://www.boost.org/doc/libs/1_69_0/libs/gil/doc/html/io.html

You can click on the header (Boost.GIL title image) and this takes you back to the main page, but it might be a little confusing especially for someone who is used to seeing the 4-button nav bars present on other boost docs, like this one:
https://www.boost.org/doc/libs/master/libs/beast/doc/html/beast/using_io/layered_streams/counted_stream_example_new.html